Buggy code:
public class Beki { private Parser parser ; private Source source ; private ICode iCode ; private SymTabStack symTabStack ; private Backend backend ; public Beki ( String operation , String filePath , String flags ) { } private static final String FLAGS = "[-ix]" ; private static final String USAGE = ( "Usage:<seq2seq4repair_space>Beki<seq2seq4repair_space>execute|compile<seq2seq4repair_space>" + ( Beki . FLAGS ) ) + "<seq2seq4repair_space><source<seq2seq4repair_space>file<seq2seq4repair_space>path>" ; private static Scanner scanner = new Scanner ( System . in ) ; public static void main ( String [ ] args ) { } private static final String SOURCE_LINE_FORMAT = "%03d<seq2seq4repair_space>%s" ; private class SourceMessageListener implements MessageListener { @ Override public void messageReceived ( Message message ) { MessageType . MessageType type = message . getType ( ) ; Object [ ] body = ( ( Object [ ] ) ( message . getBody ( ) ) ) ; switch ( type ) { case SOURCE_LINE : { int lineNumber = ( ( Integer ) ( body [ 0 ] ) ) ; String lineText = ( ( String ) ( body [ 1 ] ) ) ; System . out . println ( String . format ( Beki . SOURCE_LINE_FORMAT , lineNumber , lineText ) ) ; break ; } } } } private static final String TOKEN_FORMAT = ">>><seq2seq4repair_space>%-15s<seq2seq4repair_space>line=%03d,<seq2seq4repair_space>pos=%2d,<seq2seq4repair_space>text=\"%s\"" ; private static final String VALUE_FORMAT = ">>><seq2seq4repair_space>value=%s" ; private static final String PARSER_SUMMARY_FORMAT = "\n%,20d<seq2seq4repair_space>source<seq2seq4repair_space>lines." + ( "\n%,20d<seq2seq4repair_space>syntax<seq2seq4repair_space>errors." + "\n%,20.2f<seq2seq4repair_space>seconds<seq2seq4repair_space>total<seq2seq4repair_space>parsing<seq2seq4repair_space>time.\n" ) ; private static final int PREFIX_WIDTH = 5 ; private class ParserMessageListener implements MessageListener { @ Override public void messageReceived ( Message message ) { MessageType . MessageType type = message . getType ( ) ; switch ( type ) { case TOKEN : { Object [ ] body = ( ( Object [ ] ) ( message . getBody ( ) ) ) ; int lineNumber = ( ( Integer ) ( body [ 0 ] ) ) ; int positionNumber = ( ( Integer ) ( body [ 1 ] ) ) ; TokenType tokenType = ( ( TokenType ) ( body [ 2 ] ) ) ; String tokenText = ( ( String ) ( body [ 3 ] ) ) ; Object tokenValue = body [ 4 ] ; System . out . println ( String . format ( Beki . TOKEN_FORMAT , tokenType , lineNumber , positionNumber , tokenText ) ) ; if ( tokenValue != null ) { if ( tokenType == ( BekiTokenType . STRINGCONST ) ) { tokenValue = ( "\"" + tokenValue ) + "\"" ; } System . out . println ( String . format ( Beki . VALUE_FORMAT , tokenValue ) ) ; } break ; } case SYNTAX_ERROR : { Object [ ] body = ( ( Object [ ] ) ( message . getBody ( ) ) ) ; int lineNumber = ( ( Integer ) ( body [ 0 ] ) ) ; int positionNumber = ( ( Integer ) ( body [ 1 ] ) ) ; String tokenType = ( ( String ) ( body [ 2 ] ) ) ; String errorMessage = ( ( String ) ( body [ 3 ] ) ) ; int spaceCount = ( Beki . PREFIX_WIDTH ) + positionNumber ; StringBuilder flagBuffer = new StringBuilder ( ) ; for ( int i = 1 ; i < spaceCount ; ++ i ) { flagBuffer . append ( '<seq2seq4repair_space>' ) ; } flagBuffer . append ( "^\n" ) ; <START_BUG> flagBuffer . append ( "***" ) . append ( errorMessage ) ; <END_BUG> if ( tokenType != null ) { flagBuffer . append ( "<seq2seq4repair_space>[at<seq2seq4repair_space>\"" ) . append ( tokenType ) . append ( "\"]" ) ; } System . out . println ( flagBuffer . toString ( ) ) ; break ; } case PARSER_SUMMARY : { Number [ ] body = ( ( Number [ ] ) ( message . getBody ( ) ) ) ; int statementCount = ( ( Integer ) ( body [ 0 ] ) ) ; int syntaxErrors = ( ( Integer ) ( body [ 1 ] ) ) ; float elapsedTime = ( ( Float ) ( body [ 2 ] ) ) ; System . out . println ( String . format ( Beki . PARSER_SUMMARY_FORMAT , statementCount , syntaxErrors , elapsedTime ) ) ; break ; } } } } private static final String INTERPRETER_SUMMARY_FORMAT = "\n%,20d<seq2seq4repair_space>statements<seq2seq4repair_space>executed." + ( "\n%,20d<seq2seq4repair_space>runtime<seq2seq4repair_space>errors." + "\n%,20.2f<seq2seq4repair_space>seconds<seq2seq4repair_space>total<seq2seq4repair_space>execution<seq2seq4repair_space>time.\n" ) ; private static final String COMPILER_SUMMARY_FORMAT = "\n%,20d<seq2seq4repair_space>instructions<seq2seq4repair_space>generated." + "\n%,20.2f<seq2seq4repair_space>seconds<seq2seq4repair_space>total<seq2seq4repair_space>code<seq2seq4repair_space>generation<seq2seq4repair_space>time.\n" ; private class BackendMessageListener implements MessageListener { public void messageReceived ( Message message ) { MessageType . MessageType type = message . getType ( ) ; switch ( type ) { case INTERPRETER_SUMMARY : { Number [ ] body = ( ( Number [ ] ) ( message . getBody ( ) ) ) ; int executionCount = ( ( Integer ) ( body [ 0 ] ) ) ; int runtimeErrors = ( ( Integer ) ( body [ 1 ] ) ) ; float elapsedTime = ( ( Float ) ( body [ 2 ] ) ) ; System . out . printf ( Beki . INTERPRETER_SUMMARY_FORMAT , executionCount , runtimeErrors , elapsedTime ) ; break ; } case COMPILER_SUMMARY : { Number [ ] body = ( ( Number [ ] ) ( message . getBody ( ) ) ) ; int instructionCount = ( ( Integer ) ( body [ 0 ] ) ) ; float elapsedTime = ( ( Float ) ( body [ 1 ] ) ) ; System . out . printf ( Beki . COMPILER_SUMMARY_FORMAT , instructionCount , elapsedTime ) ; break ; } } } } }

Fix:
flagBuffer . append ( "***" ) . append ( errorMessage ) . append ( "<seq2seq4repair_space>line<seq2seq4repair_space>=<seq2seq4repair_space>" ) . append ( lineNumber ) . append ( "<seq2seq4repair_space>pos<seq2seq4repair_space>=<seq2seq4repair_space>" ) . append ( positionNumber ) ;